1. Field of the Invention
The present invention relates to a color image sensing device, and more particularly to a CIS (CMOS image sensor) type color image sensing device capable of summing up pixel data representing the same color and outputting the summed pixel data, and a pixel data reading method thereof.
2. Description of the Related Art
A color image sensing device converts an image into an electric signal and transmits the image to a screen. Color image sensing devices typically include a digital still camera for reproducing a still image and a camcorder for reproducing a moving image.
Color image sensing devices having an image sensor for converting light into an electric signal can be classified into CCD (Charge Coupled Device) types and CIS (Contact Image Sensor) types depending on the type of the image sensor. The CCD type image sensing devices are designed for a wide range of color image sensing applications and include a CCD image sensor. The CCD image sensor converts external light into an electric signal using a plurality of MOS (Metal Oxide Semiconductor) capacitors arranged on a semiconductor substrate. The CIS type image sensing device includes a CMOS (Complementary Metal Oxide Semiconductor) image sensor that converts photogenerated charge to voltage inside each pixel using a plurality of CMOS transistors formed on a semiconductor substrate.
FIG. 1 is a block diagram of a conventional image sensing device 101. Referring to FIG. 1, the color image sensing device 101 includes an APS (Active Pixel Sensor) array 111, a row driver 121, first and second data processors 131 and 132, and a multiplexer 141. The APS array 111 includes a plurality of column arrays 111a through 111h and vertical transfer lines 115. When the row driver 121 addresses the pixels R11 through G88, data is output from the addressed pixels. As shown in FIG. 1, data output from the column arrays 111a, 111c, 111e and 111g is transmitted to the second data processor 132 and data output from the column arrays 111b, 111d, 111f and 111h is transmitted to the first data processor 131. The first and second data processors 131 and 132 amplify the data as input thereto, convert the amplified data into digital data and transmit the digital data to the multiplexer 141. The multiplexer 141 receives separate digital data streams from the first and second data processors 131 and 132 and combines them into one data stream.
FIG. 2 illustrates an arrangement of pixels from which data is read when the color image sensing device 101 of FIG. 1 is operated in a moving image mode. Referring to FIG. 2, the data of neighboring four pixels is grouped together and read when the color image sensing device 101 is operated in the moving image mode.
In a megapixel color image sensing device 101, the data read from the pixels R11 through G88 can be output to reproduce an image with high resolution in a still image mode. When the color image sensing device 101 is operated in the moving image mode, an image can be reproduced with low resolution to obtain a smooth moving image.
To reproduce a smooth moving image when the color image sensing device 101 is operated in the moving image mode, a method of skipping pixels at a predetermined rate can be used when the pixels are addressed, as shown in FIG. 2. In this case, however, the device performance can be degraded by the aliasing noise as a result of the narrow spatial sampling window, the reduced optical efficiency and poorer S/N ratio.